Resonator Devices with Reverse Polarized Layers

The present disclosure relates, in general, to resonator devices for use in various types of electronic circuits and electronic devices. For example, resonator devices can be used in various filtering applications pertaining to different types of signals, including filters for radio frequency (RF) signals and other types of signals. Advancements in resonator device technology including bulk acoustic wave (BAW) resonator devices are desired in various applications.

In the following description, for the purposes of explanation, numerous details are set forth to provide a thorough understanding of the disclosure. It will be apparent to one skilled in the art, however, that other aspects can be practiced without some details. Different examples are described herein, and while various features are ascribed to the examples, it should be appreciated that the features described with respect to one example may be incorporated with other examples as well. By the same token, however, no single feature or features of any described example should be considered essential to every example, as other examples may omit such features.

When an element is referred to herein as being “connected” or “coupled” to another element, it is to be understood that the elements can be directly connected to the other element, or have intervening elements present between the elements. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, it should be understood that no intervening elements are present in the “direct” connection between the elements. However, the existence of a direct connection does not exclude other connections, in which intervening elements may be present.

When an element is referred to herein as being “disposed” in some manner relative to another element (e.g., disposed on, disposed between, disposed under, disposed adjacent to, or disposed in some other relative manner), it is to be understood that the elements can be directly disposed relative to the other element (e.g., disposed directly on another element), or have intervening elements present between the elements. In contrast, when an element is referred to as being “disposed directly” relative to another element, it should be understood that no intervening elements are present in the “direct” example. However, the existence of a direct disposition does not exclude other examples in which intervening elements may be present.

Likewise, when an element is referred to herein as being a “layer”, it is to be understood that the layer can be a single layer or include multiple layers. For example, a conductive layer can include multiple different conductive materials or multiple layers of different conductive materials, and a dielectric layer may comprise multiple dielectric materials or multiple layers of dielectric materials. When a layer is described as being coupled or connected to another layer, it is to be understood that the coupled or connected layers may include intervening elements present between the coupled or connected layers. In contrast, when a layer is referred to as being “directly” connected or coupled to another layer, it should be understood that no intervening elements are present between the layers. However, the existence of directly coupled or connected layers does not exclude other connections in which intervening elements may be present.

Moreover, the terms left, right, front, back, top, bottom, forward, reverse, clockwise and counterclockwise are used for purposes of explanation only and are not limited to any fixed direction or orientation. Rather, they are used merely to indicate relative locations and/or directions between various parts of an object and/or components.

Furthermore, unless otherwise indicated, all numbers used herein to express quantities, dimensions, and so forth should be understood as being modified in all instances by the term “about”. In this application, the use of the singular includes the plural unless specifically stated otherwise, and use of the terms “and” and “or” means “and/or” unless otherwise indicated. Moreover, the use of the terms “including” and “having”, as well as other forms, such as “includes”, “included”, “has”, “have”, and “had”, should be considered non-exclusive. Also, terms such as “element” or “component” encompass both elements and components comprising one unit and elements and components that comprise more than one unit, unless specifically stated otherwise.

While some features and aspects have been described with respect to the examples, one skilled in the art will recognize that numerous modifications are possible. For example, the methods and processes described herein may be implemented using hardware components, custom integrated circuits (ICs), programmable logic, and/or any combination thereof. Further, while various methods and processes described herein may be described with respect to particular structural and/or functional components for ease of description, methods provided by various embodiments are not limited to any particular structural and/or functional architecture but instead can be implemented in any suitable hardware configuration. Similarly, while some functionality is ascribed to one or more system components, unless the context dictates otherwise, this functionality can be distributed among various other system components in accordance with the several embodiments.

Moreover, while the procedures of the methods and processes described herein are described in a particular order for ease of description, unless the context dictates otherwise, various procedures may be reordered, added, and/or omitted in accordance with various implementations. Moreover, the procedures described with respect to one method or process may be incorporated within other described methods or processes; likewise, system components described according to a particular structural architecture and/or with respect to one system may be organized in alternative structural architectures and/or incorporated within other described systems. Hence, while various examples are described with or without some features for ease of description and to illustrate aspects of those embodiments, the various components and/or features described herein with respect to a particular example can be substituted, added and/or subtracted from among other described embodiments, unless the context dictates otherwise. Consequently, although several examples are described above, it will be appreciated that the disclosure is intended to cover all modifications and equivalents within the scope of the following claims.

Referring to, a cross section illustrating an example resonator deviceis shown, in accordance with some aspects of the disclosure. The resonator devicegenerally is similar to a thin-film bulk acoustic resonator (FBAR) device and can be used, for example, in a variety of electronic circuits and electronic devices for BAW applications (e.g., RF filters, duplexers, RF power amplifiers, RF receiver modules, etc.). However, relative to a typical FBAR device, the resonator deviceincludes two piezoelectric film layers instead of one piezoelectric film layer. Accordingly, the resonator devicecan be considered the second thickness extensional (TE) mode with a polarization-switched bulk acoustic resonator device that includes a stack of layers. As illustrated in, the resonator deviceincludes a top electrode, a bottom electrode, a middle material, a piezoelectric film, and a piezoelectric film. The top electrodecan be coupled to an input signal(e.g., an RF signal, etc.), and the bottom electrodecan then be coupled to a reference voltage(i.e., the bottom electrodecan be grounded). These connections can also be reversed such that the top electrodecan be coupled to the reference voltageand the bottom electrodecan be coupled to the input signal.

The top electrodeand the bottom electrodecan be formed using various suitable materials depending on the application. For example, the top electrodecan be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The bottom electrodecan likewise be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The top electrodeand/or the bottom electrodecan also be formed using lighter materials in some applications such as, for example, materials that are not necessarily metals. Notably, relative to alternative structures, only the bottom electrodeis grounded, and the top electrodeis coupled to the input signal(or the reverse). Due to this configuration, the piezoelectric filmand the piezoelectric filmare not connected in parallel, but in series. To keep a similar impedance as an FBAR device, the active area of the resonator deviceis nearly doubled compared to an FBAR device, and the TEstack can cancel the second harmonics completely at the condition the stack is symmetric, and one piezoelectric layer has the polarization reversed compared to the other piezoelectric layer.

The middle materialcan also be formed using various suitable materials depending on the application. For example, the middle materialcan be a middle electrode formed using suitable metals such as aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The middle materialcan also be formed using lighter materials (including non-metals) in some applications. The middle materialis disposed between the piezoelectric filmand the piezoelectric film, and the middle materialcan be constructed such that the middle materialdoes not acoustically decouple the piezoelectric filmand the piezoelectric film(e.g., like in a coupled resonator filter (CRF) where decoupling layer(s) are included between piezoelectric layer(s)). Instead, the piezoelectric filmand the piezoelectric filmcan be tightly coupled acoustically to form a single resonator device with one series resonance and one parallel resonance. The composition and the thickness of the middle materialcan be adjusted to ensure that the resonator devicehas a Type II response.

In filtering applications, when using a Type I resonator device, the output signal can include rattles and/or other noise artifacts present at a frequency above the resonant frequency (F). This noise above Fcan be a significant drawback for filters where high energy modes land from mid-band to the high-band edge, where self-heating is most critical. Moreover, the noise above Fcan degrade linear performance on the upper band. However, when using a Type II resonator device, the output signal can include rattles and/or other noise artifacts that are present at a frequency below F. The noise below Fcan be much less critical for filtering applications, where linear and large signal response are improved. Accordingly, because the inclusion of the middle materialin the structure of the resonator devicecan make the resonator device a Type II resonator device, the inclusion of the middle materialin the structure of the resonator devicecan improve the performance of the resonator devicein many filtering applications.

The piezoelectric filmand the piezoelectric filmcan be formed using various suitable piezoelectric materials depending on the application. For example, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. Similarly, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. As shown, the piezoelectric filmhas a first polarity Pand the piezoelectric filmhas a second polarity P. The first polarity is in a first orientation and the second polarity is in a second orientation, and the first orientation is opposite the second orientation. The first polarity and the second polarity can be created in the piezoelectric filmand the piezoelectric film, respectively, by doping the piezoelectric filmand/or the piezoelectric filmwith a dopant. In the resonator device, the dipole moment of the piezoelectric filmand the dipole moment of the piezoelectric filmcan generally be reversed relative to each other.

For example, the piezoelectric filmcan be deposited on the bottom electrodeas either N-polar or M-polar. The piezoelectric filmcan then be deposited in the same manner as the piezoelectric filmon the middle materialsuch that the piezoelectric filminitially is polarized in the same orientation as the piezoelectric film. However, then the piezoelectric filmcan be doped with a suitable dopant to reverse the polarization of the piezoelectric filmrelative to the piezoelectric film(e.g., to be M-polar if the piezoelectric filmis N-polar, to be N-polar if the piezoelectric filmis M-polar, etc.). The dopant can be any of a variety of suitable dopants, such as, for example, silicon, germanium, magnesium, copper, aluminum, a combination of silicon and magnesium, a combination of magnesium with one or more additional elements, and/or other suitable dopants. The piezoelectric filmcan be disposed between the top electrodeand the bottom electrode, and the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode. In some applications, the piezoelectric filmcan be doped with the dopant instead of the piezoelectric film. Also, in some applications, both the piezoelectric filmand the piezoelectric filmcan be doped with suitable dopants to induce the reversed polarity of the piezoelectric filmand the piezoelectric film.

In some alternative approaches, reversed polarity of the piezoelectric filmand the piezoelectric filmcan be induced by applying an external electrical field (e.g., DC field) across one of the piezoelectric filmor the piezoelectric film. However, this approach has some drawbacks due to the polarization being clamped in the grain boundaries (joints) and defects (e.g., vacancy, atom interstitial). Thus, the polarities may be unable to be switched entirely. Moreover, in a large wafer, it may be impractical to flip the polarization of all resonators in this manner without experiencing some level of performance degradation due to residual effects. However, by flipping the polarities using doping as in the resonator device, advantages relative to the external electrical field approach can be provided. For example, a more reliable polarity reversing can be provided because polarity can be reversed in all domains, and thus a better homogeneity of the reversed films can be provided across a large wafer. Further, since no external electrical field needs to be provided, the middle materialcan be formed using materials besides metals, such as discussed above, including materials with a positive temperature compensation.

Moreover, in many resonator applications, the resonant frequency (F) is inversely proportional to the thickness of the layers of the resonator device. As a result, for higher frequency applications, the thickness of the layers of the resonator device need to get smaller and smaller. For high frequency applications involving frequencies of 7-8 GHz or higher, a more traditional FBAR device including only one piezoelectric film layer would need to be so thin, and the overall area of the device would need to be so small, that the device cannot practically be used in these applications. When considering even higher frequency applications such as satellite applications involving frequencies in the 12-18 GHz range, more traditional FBAR devices become even less practical. However, the resonator devicecan provide around twice the frequency of a single piezoelectric layer FBAR device with around the same active stack thickness. The resonator devicecan operate at high frequencies (e.g., above 10 GHz) with very good resistive loss, and the resonator devicecan cancel the undesired Tand Tmodes (e.g., the closest TEand/or TEmodes), thereby leaving only the TE(n=2) mode of interest. Additionally, the TEmode common in FBAR devices for lower frequency applications can be eliminated by using the resonator device.

Additionally, the piezoelectric filmand the piezoelectric filmcan be symmetric (e.g., the same composition and thickness as measured between adjacent piezoelectric layers in the stack) or asymmetric (e.g., different composition such as thickness and/or material properties such as acoustic velocity, piezoelectric constant, etc.) as long as they satisfy the condition that the polarity orientations are reversed relative to each other. In cases where the piezoelectric filmand the piezoelectric filmare symmetric, the resonator devicecan advantageously provide only the second overtone (TEmode). However, when the piezoelectric filmand the piezoelectric filmare asymmetric, the resonator devicecan provide the second overtone and associated advantages, but also may provide residual (parasitic) modes such as TEand/or TEovertones.

Referring to, a cross section illustrating another example resonator deviceis shown, in accordance with some aspects of the disclosure. The resonator devicegenerally is similar to the resonator device. However, relative to the resonator device, the resonator devicedoes not include a middle layer between piezo layers. Due to the absence of the middle layer, the resonator devicegenerally is a Type I resonator device instead of a Type II resonator device, and can provide advantages in different applications. The resonator devicecan also be considered a TEdevice that includes a stack of layers. As illustrated in, the resonator deviceincludes a top electrode, a bottom electrode, a piezoelectric film, and a piezoelectric film. The top electrodecan be coupled to an input signal(e.g., an RF signal, etc.), and the bottom electrodecan then be coupled to a reference voltage(i.e., the bottom electrodecan be grounded). These connections can also be reversed such that the top electrodecan be coupled to the reference voltageand the bottom electrodecan be coupled to the input signal.

The top electrodeand the bottom electrodecan be formed using various suitable materials depending on the application. For example, the top electrodecan be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The bottom electrodecan likewise be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The top electrodeand/or the bottom electrodecan also be formed using lighter materials in some applications such as, for example, materials that are not necessarily metals. Notably, relative to alternative structures, only the bottom electrodeis grounded, and the top electrodeis coupled to the input signal(or the reverse). Due to this configuration, the piezoelectric filmand the piezoelectric filmare not connected in parallel, but in series.

The piezoelectric filmand the piezoelectric filmcan be formed using various suitable piezoelectric materials depending on the application. For example, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. Similarly, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. As shown, the piezoelectric filmhas a first polarity Pand the piezoelectric filmhas a second polarity P. The first polarity is in a first orientation and the second polarity is in a second orientation, and the first orientation is opposite the second orientation. The first polarity and the second polarity can be created in the piezoelectric filmand the piezoelectric film, respectively, by doping the piezoelectric filmand/or the piezoelectric filmwith a dopant. In the resonator device, the dipole moment of the piezoelectric filmand the dipole moment of the piezoelectric filmcan generally be reversed relative to each other.

For example, the piezoelectric filmcan be deposited on the bottom electrodeas either N-polar or M-polar. The piezoelectric filmcan then be deposited in the same manner as the piezoelectric filmon the piezoelectric filmsuch that the piezoelectric filminitially is polarized in the same orientation as the piezoelectric film. However, then the piezoelectric filmcan be doped with a suitable dopant to reverse the polarization of the piezoelectric filmrelative to the piezoelectric film(e.g., to be M-polar if the piezoelectric filmis N-polar, to be N-polar if the piezoelectric filmis M-polar, etc.). The dopant can be any of a variety of suitable dopants, such as, for example, silicon, germanium, magnesium, copper, aluminum, a combination of silicon and magnesium, a combination of magnesium with one or more additional elements, and/or other suitable dopants. The piezoelectric filmcan be disposed between the top electrodeand the bottom electrode, and the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode.

The piezoelectric filmand the piezoelectric filmcan be symmetric (e.g., the same composition and thickness as measured between adjacent piezoelectric layers in the stack) or asymmetric (e.g., different composition such as thickness and/or material properties such as acoustic velocity, piezoelectric constant, etc.) as long as they satisfy the condition that the polarity orientations are reversed relative to each other. In cases where the piezoelectric filmand the piezoelectric filmare symmetric, the resonator devicecan advantageously provide only the second overtone (TEmode). However, when the piezoelectric filmand the piezoelectric filmare asymmetric, the resonator devicecan provide the second overtone and associated advantages, but also may provide residual (parasitic) modes such as TEand/or TEovertones. Like the resonator device, the resonator devicecan provide around twice the frequency of a single piezoelectric layer FBAR device with around the same active stack thickness.

Referring to, a cross section illustrating another example resonator deviceis shown, in accordance with some aspects of the disclosure. The resonator devicegenerally is similar to the resonator device. However, relative to the resonator device, the resonator deviceincludes three piezoelectric film layers instead of two piezoelectric film layers to provide added suitability for high frequency applications, for example. Accordingly, the resonator devicecan be considered the third thickness extensional (TE) mode with a polarization-switched bulk acoustic resonator device that includes a stack of layers. As illustrated in, the resonator deviceincludes a top electrode, a bottom electrode, a middle material, a middle material, a piezoelectric film, a piezoelectric film, and a piezoelectric film. The top electrodecan be coupled to an input signal(e.g., an RF signal, etc.), and the bottom electrodecan then be coupled to a reference voltage(i.e., the bottom electrodecan be grounded). These connections can also be reversed such that the top electrodecan be coupled to the reference voltageand the bottom electrodecan be coupled to the input signal.

The top electrodeand the bottom electrodecan be formed using various suitable materials depending on the application. For example, the top electrodecan be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The bottom electrodecan likewise be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The top electrodeand/or the bottom electrodecan also be formed using lighter materials in some applications such as, for example, materials that are not necessarily metals. Notably, relative to alternative structures, only the bottom electrodeis grounded, and the top electrodeis then coupled to the input signal(or the reverse). As a result, the piezoelectric film, the piezoelectric film, and the piezoelectric filmare not connected in parallel, but in series.

The middle materialand the middle materialcan also be formed using various suitable materials depending on the application. For example, the middle materialcan be a middle electrode formed using various suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The middle materialcan also be formed using lighter materials (including non-metals) in some applications. The middle materialcan likewise be a middle electrode formed using various suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The middle materialcan also be formed using lighter materials (including non-metals) in some applications. The middle materialis disposed between the piezoelectric filmand the piezoelectric film, and the middle materialis disposed between the piezoelectric filmand the piezoelectric film. The middle materialand the middle materialcan be constructed such that the middle materialand the middle materialdo not acoustically decouple the piezoelectric film, the piezoelectric film, and the piezoelectric film(e.g., like in a CRF where decoupling layer(s) are included between piezoelectric layer(s)). The piezoelectric film, the piezoelectric film, and the piezoelectric filminstead can be tightly coupled acoustically to form a single resonator device with one series resonance and one parallel resonance. The composition and the thickness of the middle materialand the middle materialcan be adjusted to ensure that the resonator devicehas a Type II response.

The piezoelectric film, the piezoelectric film, and the piezoelectric filmcan be formed using various suitable piezoelectric materials depending on the application. For example, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. Similarly, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. The piezoelectric filmcan also be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. As shown, the piezoelectric filmhas a first polarity P, the piezoelectric filmhas a second polarity P, and the piezoelectric filmhas a third polarity P. The first polarity and the third polarity are in a first orientation and the second polarity is in a second orientation, where the first orientation is opposite the second orientation.

The first polarity, the second polarity, and/or the third polarity can be created in the piezoelectric film, the piezoelectric film, and/or the piezoelectric film, respectively, by doping the piezoelectric film, the piezoelectric film, and/or the piezoelectric filmwith a dopant. For example, the piezoelectric film, the piezoelectric film, and the piezoelectric filmcan all be deposited as M-polar, and then the piezoelectric filmcan de doped with a suitable dopant to reverse the polarization of the piezoelectric filmto be N-polar. The dopant can be any of a variety of suitable dopants, such as, for example, silicon, germanium, magnesium, copper, aluminum, a combination of silicon and magnesium, a combination of magnesium with one or more additional elements, and/or other suitable dopants. The piezoelectric filmcan be disposed between the top electrodeand the bottom electrode, the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode, and the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode.

The piezoelectric film, the piezoelectric film, and the piezoelectric filmcan be symmetric (e.g., the same composition and thickness as measured between adjacent piezoelectric layers in the stack) or they can be asymmetric (e.g., different composition such as thickness and/or material properties such as acoustic velocity, piezoelectric constant, etc.) as long as they satisfy the condition that the polarity orientations are reversed relative to each other. In cases where the piezoelectric film, the piezoelectric film, and the piezoelectric filmare symmetric, the resonator devicecan advantageously provide only the third overtone (TEmode). However, when the piezoelectric film, the piezoelectric film, and the piezoelectric filmare asymmetric, the resonator devicecan provide the third overtone and associated advantages, but also may provide residual (parasitic) modes such as TE, TE, and/or TEovertones. The resonator devicecan provide around three times the frequency of a single piezoelectric layer FBAR device with around the same active stack thickness.

Referring to, a cross section illustrating another example resonator deviceis shown, in accordance with some aspects of the disclosure. The resonator devicegenerally is similar to the resonator device. However, relative to the resonator device, the resonator devicedoes not include middle layers between piezo layers. Due to the absence of the middle layers, the resonator devicegenerally is a Type I resonator device instead of a Type II resonator device, and can provide advantages in different applications. The resonator devicecan also be considered a TEdevice that includes a stack of layers. As illustrated in, the resonator deviceincludes a top electrode, a bottom electrode, a piezoelectric film, a piezoelectric film, and a piezoelectric film. The top electrodecan be coupled to an input signal(e.g., an RF signal, etc.), and the bottom electrodecan then be coupled to a reference voltage(i.e., the bottom electrodecan be grounded). These connections can also be reversed such that the top electrodecan be coupled to the reference voltageand the bottom electrodecan be coupled to the input signal.

The top electrodeand the bottom electrodecan be formed using various suitable materials depending on the application. For example, the top electrodecan be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The bottom electrodecan likewise be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The top electrodeand/or the bottom electrodecan also be formed using lighter materials in some applications such as, for example, materials that are not necessarily metals. Notably, relative to alternative structures, only the bottom electrodeis grounded, and the top electrodeis then coupled to the input signal(or the reverse). As a result, the piezoelectric film, the piezoelectric film, and the piezoelectric filmare not connected in parallel, but in series.

The piezoelectric film, the piezoelectric film, and the piezoelectric filmcan be formed using various suitable piezoelectric materials depending on the application. For example, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. Similarly, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. The piezoelectric filmcan also be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. As shown, the piezoelectric filmhas a first polarity P, the piezoelectric filmhas a second polarity P, and the piezoelectric filmhas a third polarity P. The first polarity and the third polarity are in a first orientation and the second polarity is in a second orientation, where the first orientation is opposite the second orientation.

The first polarity, the second polarity, and/or the third polarity can be created in the piezoelectric film, the piezoelectric film, and/or the piezoelectric film, respectively, by doping the piezoelectric film, the piezoelectric film, and/or the piezoelectric filmwith a dopant. For example, the piezoelectric film, the piezoelectric film, and the piezoelectric filmcan all be deposited as N-polar, and then the piezoelectric filmcan de doped with a suitable dopant to reverse the polarization of the piezoelectric filmto be M-polar. The dopant can be any of a variety of suitable dopants, such as, for example, silicon, germanium, magnesium, copper, aluminum, a combination of silicon and magnesium, a combination of magnesium with one or more additional elements, and/or other suitable dopants. The piezoelectric filmcan be disposed between the top electrodeand the bottom electrode, the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode, and the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode.

The piezoelectric film, the piezoelectric film, and the piezoelectric filmcan be symmetric (e.g., the same composition and thickness as measured between adjacent piezoelectric layers in the stack) or they can be asymmetric (e.g., different composition such as thickness and/or material properties such as acoustic velocity, piezoelectric constant, etc.) as long as they satisfy the condition that the polarity orientations are reversed relative to each other. In cases where the piezoelectric film, the piezoelectric film, and the piezoelectric filmare symmetric, the resonator devicecan advantageously provide only the third overtone (TEmode). However, when the piezoelectric film, the piezoelectric film, and the piezoelectric filmare asymmetric, the resonator devicecan provide the third overtone and associated advantages, but also may provide residual (parasitic) modes such as TE, TE, and/or TEovertones. The resonator devicecan provide around three times the frequency of a single piezoelectric layer FBAR device with around the same active stack thickness.

Referring to, a cross section illustrating another example resonator deviceis shown, in accordance with some aspects of the disclosure. The resonator devicegenerally is similar to the resonator device. However, relative to the resonator device, the resonator deviceincludes four piezoelectric film layers instead of two piezoelectric film layers to provide added suitability for high frequency applications, for example. Accordingly, the resonator devicecan be considered the fourth thickness extensional (TE) mode with a polarization-switched bulk acoustic resonator device that includes a stack of layers. As illustrated in, the resonator deviceincludes a top electrode, a bottom electrode, a middle material, a middle material, a middle material, a piezoelectric film, a piezoelectric film, a piezoelectric film, and a piezoelectric film. The top electrodecan be coupled to an input signal(e.g., an RF signal, etc.), and the bottom electrodecan then be coupled to a reference voltage(i.e., the bottom electrodecan be grounded). These connections can also be reversed such that the top electrodecan be coupled to the reference voltageand the bottom electrodecan be coupled to the input signal.

The top electrodeand the bottom electrodecan be formed using various suitable materials depending on the application. For example, the top electrodecan be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The bottom electrodecan likewise be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The top electrodeand/or the bottom electrodecan also be formed using lighter materials in some applications such as, for example, materials that are not necessarily metals. Notably, relative to alternative structures, only the bottom electrodeis grounded, and the top electrodeis then coupled to the input signal(or the reverse). As a result, the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmare not connected in parallel, but in series.

The middle material, the middle material, and the middle materialcan also be formed using various suitable materials depending on the application. For example, the middle materialcan be a middle electrode formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The middle materialcan also be formed using lighter materials (including non-metals) in some applications. The middle materialcan likewise be a middle electrode formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The middle materialcan also be formed using lighter materials (including non-metals) in some applications. The middle materialalso can be a middle electrode formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The middle materiallikewise can be formed using lighter materials (including non-metals) in some applications.

The middle materialis disposed between the piezoelectric filmand the piezoelectric film, the middle materialis disposed between the piezoelectric filmand the piezoelectric film, and the middle materialis disposed between the piezoelectric filmand the piezoelectric film. The middle material, the middle material, and the middle materialcan be constructed in a manner such that the middle material, the middle material, and the middle materialdo not acoustically decouple the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric film(e.g., like in a CRF where decoupling layer(s) are included between piezoelectric layer(s)). The piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filminstead can be tightly coupled acoustically to form a single resonator device with one series resonance and one parallel resonance. The composition and the thickness of the middle material, the middle material, and the middle materialcan be adjusted to ensure that the resonator devicehas a Type II response. The piezoelectric filmcan be disposed between the top electrodeand the bottom electrode, the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode, the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode, and the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode.

The piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmcan be formed using various suitable piezoelectric materials depending on the application. For example, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. Similarly, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. The piezoelectric filmalso can be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. The piezoelectric filmalso can be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. As shown, the piezoelectric filmhas a first polarity P, the piezoelectric filmhas a second polarity P, the piezoelectric filmhas a third polarity P, and the piezoelectric filmhas a fourth polarity P. The first polarity and the third polarity are in a first orientation, the second polarity and the fourth polarity are in a second orientation, and the first orientation is opposite the second orientation.

The first polarity, the second polarity, the third polarity, and/or the fourth polarity can be created in the piezoelectric film, the piezoelectric film, the piezoelectric film, and/or the piezoelectric film, respectively, by doping the piezoelectric film, the piezoelectric film, the piezoelectric film, and/or the piezoelectric filmwith a dopant. For example, the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmcan all be deposited as M-polar, and then the piezoelectric filmand the piezoelectric filmcan de doped with a suitable dopant to reverse the polarizations of the piezoelectric filmand the piezoelectric filmto be N-polar. The dopant can be any of a variety of suitable dopants, such as, for example, silicon, germanium, magnesium, copper, aluminum, a combination of silicon and magnesium, a combination of magnesium with one or more additional elements, and/or other suitable dopants.

The piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmcan be symmetric (e.g., the same composition and thickness as measured between adjacent piezoelectric layers in the stack) or asymmetric (e.g., different composition such as thickness and/or material properties such as acoustic velocity, piezoelectric constant, etc.) as long as they satisfy the condition that the polarity orientations are reversed relative to each other. In cases where the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmare symmetric, the resonator devicecan advantageously provide only the fourth overtone (TEmode). However, when the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmare asymmetric, the resonator devicecan provide the fourth overtone and associated advantages, but also may provide residual (parasitic) modes such as TEand/or TEovertones. The resonator devicecan provide around four times the frequency of a single piezoelectric layer FBAR device with around the same active stack thickness.

Referring to, a cross section illustrating another example resonator deviceis shown, in accordance with some aspects of the disclosure. The resonator devicegenerally is similar to the resonator device. However, relative to the resonator device, the resonator devicedoes not include middle layers between piezo layers. Due to the absence of the middle layers, the resonator devicegenerally is a Type I resonator device instead of a Type II resonator device, and can provide advantages in different applications. The resonator devicecan also be considered a TEdevice that includes a stack of layers. As illustrated in, the resonator deviceincludes a top electrode, a bottom electrode, a piezoelectric film, a piezoelectric film, a piezoelectric film, and a piezoelectric film. The top electrodecan be coupled to an input signal(e.g., an RF signal, etc.), and the bottom electrodecan then be coupled to a reference voltage(i.e., the bottom electrodecan be grounded). These connections can also be reversed such that the top electrodecan be coupled to the reference voltageand the bottom electrodecan be coupled to the input signal.

The top electrodeand the bottom electrodecan be formed using various suitable materials depending on the application. For example, the top electrodecan be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The bottom electrodecan likewise be formed using suitable metals such as, for example, aluminum, copper, molybdenum, tungsten, platinum, iridium, and/or other suitable metals. The top electrodeand/or the bottom electrodecan also be formed using lighter materials in some applications such as, for example, materials that are not necessarily metals. Notably, relative to alternative structures, only the bottom electrodeis grounded, and the top electrodeis then coupled to the input signal(or the reverse). As a result, the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmare not connected in parallel, but in series.

The piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmcan be formed using various suitable piezoelectric materials depending on the application. For example, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. Similarly, the piezoelectric filmcan be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. The piezoelectric filmalso can be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. The piezoelectric filmalso can be formed using aluminum nitride, scandium aluminum nitride, zinc oxide, lead zirconate titanate, barium strontium titanate, lithium tantalate, lithium niobate, and/or other suitable piezoelectric materials. As shown, the piezoelectric filmhas a first polarity P, the piezoelectric filmhas a second polarity P, the piezoelectric filmhas a third polarity P, and the piezoelectric filmhas a fourth polarity P. The first polarity and the third polarity are in a first orientation, the second polarity and the fourth polarity are in a second orientation, and the first orientation is opposite the second orientation.

The first polarity, the second polarity, the third polarity, and/or the fourth polarity can be created in the piezoelectric film, the piezoelectric film, the piezoelectric film, and/or the piezoelectric film, respectively, by doping the piezoelectric film, the piezoelectric film, the piezoelectric film, and/or the piezoelectric filmwith a dopant. For example, the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmcan all be deposited as N-polar, and then the piezoelectric filmand the piezoelectric filmcan de doped with a suitable dopant to reverse the polarizations of the piezoelectric filmand the piezoelectric filmto be M-polar. The dopant can be any of a variety of suitable dopants, such as, for example, silicon, germanium, magnesium, copper, aluminum, a combination of silicon and magnesium, a combination of magnesium with one or more additional elements, and/or other suitable dopants. The piezoelectric filmcan be disposed between the top electrodeand the bottom electrode, the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode, the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode, and the piezoelectric filmcan be disposed between the piezoelectric filmand the top electrode.

The piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmcan be symmetric (e.g., the same composition and thickness as measured between adjacent piezoelectric layers in the stack) or asymmetric (e.g., different composition such as thickness and/or material properties such as acoustic velocity, piezoelectric constant, etc.) as long as they satisfy the condition that the polarity orientations are reversed relative to each other. In cases where the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmare symmetric, the resonator devicecan advantageously provide only the fourth overtone (TEmode). However, when the piezoelectric film, the piezoelectric film, the piezoelectric film, and the piezoelectric filmare asymmetric, the resonator devicecan provide the fourth overtone and associated advantages, but also may provide residual (parasitic) modes such as TEand/or TEovertones. The resonator devicecan provide around four times the frequency of a single piezoelectric layer FBAR device with around the same active stack thickness.